Plastic transmission filter

ABSTRACT

A plastic transmission filter ( 1 ) composed of mating upper ( 2 ) and lower ( 3 ) shells of synthetic resin material with at least one set of registering weld posts ( 10 ) extending between inner surfaces of the upper and lower shells; a fluid pervious centertube ( 4 ) interposed between the mating shells around the weld posts, and a filter material ( 5 ) wrapped around the centertube to form a bag filter. The filter assembly can be welded together in a single vibration welding operation and provides enhanced flow of transmission fluid by avoiding flow restrictions caused by prior art reinforcement poles.

BACKGROUND OF THE INVENTION

Plastic transmission filters are used in approximately 10% of the Carindustry. The current plastic transmission filter used in the marketrequires a complex assembly process. In addition, current transmissionfilter designs cause a very high pressure drop across the filterassembly, resulting in pump cavitation.

The current plastic transmission filter assembly process requires thefilter media to be welded or glued to the filter lower shell at thefluid inlet, and then the upper shell is subsequently welded to thelower shell. This requires two welding processes, which adds bothinconvenience and expense to the manufacturing process.

The plastic transmission filter housing has a tendency to collapse fromthe pressure drop during cold flow. The conventional solution in themarket has been to add poles to the upper shell and lower shell toprevent the filter housing from collapsing. However this solution causesa problem by pintching the media at the poles, resulting in increasedflow restriction inside the filter.

SUMMARY OF THE INVENTION

The plastic transmission filter of the present invention is unique fortwo reasons. First, the design allows us to assemble the filter in asingle welding operation. Second, the design allows better flow bydecreasing the flow restriction in the filter assembly. The designfeatures responsible for these improvements are the centertube and weldposts located at fluid inlet.

The weld posts and the centertube are advantageous in two ways. First,the centertube and weld posts increase the structural strength insidethe filter. This results in minimizing the filter collapse at cold flowpressure drop. Second, the centertube and weld posts provide decreasedflow resistance and increased flow by eliminating the previously usedpoles which caused flow restrictions by pinching the filter medium.

The transmission filter of the present invention can be used in alltypes of automotive transmissions which require fluid filtration, aswell as in other filtration applications.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in further detail hereinafter withreference to illustrative preferred embodiments shown in theaccompanying drawings in which:

FIG. 1 is an exploded perspective view of a filter according to theinvention;

FIG. 2 is a vertical sectional view of an assembled filter according tothe invention;

FIG. 3 is a cross-sectional view showing how the filter material isclamped between the upper and lower shells and the centertube to form abag filter; and

FIGS. 4A through 4E illustrate the assemply of the transmission filterof the inveniton.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows an exploded view of a transmission filter 1 according tothe present invention. The filter 1 comprises an upper shell 2 and alower shell 3, each molded from a suitable synthetic resin material. Anexample of a suitable material is a glass fiber reinforced polyamideplastic known as PA66GF33, which signifies a nylon 66 resin reinforcedwith 33% glass fibers. Upper shell 2 and lower shell 3 mate together toform a filter housing. The two shells are each provided in a centralregion with a plurality of registering welding posts 10 which engageeach other to prevent the housing from collapsing when the filter issubjected to a high pressure differential.

Further reinforcement is provided by an open mesh centertube 4 which isalso interposed between upper shell 2 and lower shell 3 surrounding thewelding posts 10. Centertube 4 is likewise made of thermoplasticsynthetic resin material which can be readily welded to the material ofupper and lower shells 2 and 3. Transmission fluid is drawn into thefilter housing through an inlet 6 formed in the bottom of lower shell 3which opens into centertube 4. The fluid then passes through theopenings in the mesh of the centertube into a surrounding bag filter 5.The bag filter 5 may be formed from a conventional non-woven filterfleece. After passing through the bag filter 5, the now filtered fluidexits the filter housing through an outlet 7 which communicates with apump (not shown) which pumps the fluid through the transmission circuit.

On the outside of lower shell 3 are shown two magnet support posts 9.Ring-shaped magnets 8 are disposed on these posts, and then the freeends of the posts are melted slightly to lock the annular magnets inplace. The magnets are thus mounted immersed in the transmission fluidsurrounding the filter in the transmission case where they can capturemetal particles which may be present in the fluid.

Support tabs 11 may be molded on the outer surface of lower shell 3 andsupport tabs 12 may be molded on the outer surface of upper shell 2 toassure proper positioning of the filter housing within the transmissioncase.

FIG. 2 shows the assembled transmission filter of the invention in asectional view. The registering alignment of the weld posts 10 on thethe upper and lower shells 2 and 3 can be clearly seen in the drawing.The filter media which form bag filter 5 is provided with a centralaperture through which the weld posts 10 extend, and the materialsurrounding the central aperture is clamped between the upper axial faceof centertube 4 and the adjacent inside surface of upper shell 2. Thefilter medium is then folded back over the centertube 4 and clampedbetween the lower axial face of centertube 4 and the adjacent insidesurface of lower shell 3. A through hole 16 aligned with inlet 6 isprovided in the filter medium to enable the fluid from the inlet tofreely enter the centertube.

If desired, alignment holes 15 can be formed in the filter medium to fitover the weld posts 10 inside centertube 4 to assure proper alignment ofthe filter material. The periphery of the folded filter medium isclamped between the outer flanges 13 and 14 of the respective lower andupper shells. As a result of this construction, it is possible to weldthe the upper axial face of centertube 4 to upper shell 2, the loweraxial face of centertube 4 to lower shell 3, the registering weld posts10 of the upper and lower shells 2 and 3 to each other, and the outerflanges 13 and 14 of the lower and upper shells to each other in asingle vibration welding operation with the filter media properlypositioned between the parts to form a bag filter through which thetransmission fluid must pass to move from the inlet 6 to the outlet 7.

FIG. 3 is a sectional view depicting the arrangement of the filtermedium 5 in between upper and lower shells 2 and 3 and centertube 4. Theregistering alignment of weld posts 10 on upper and lower shells 2 and 3is also illustrated. In addition, it can be clearly seen from thisfigure how weld posts 10 can be inserted through alignment holes 15 inthe filter medium 5 to assure proper positioning of the filter medium.Likewise, It can be seen how the filter medium 5 is clamped between oneaxial end face of centertube 4 and the inside surface of upper shell 2,between the other axial end face of centertube 4 and the inside surfaceof lower shell 3, and between the outer flanges 13 and 14 of lower shell3 and upper shell 2, respectively, to form a bag filter. The arrows inthe figure illustrate how fluid is drawn in through inlet opening 6 intocentertube 4, flows radially outwardly through the pervious sides ofcentertube 4 into the surrounding bag filter 5, passes through the bagfilter, and thence is discharged through outlet opening 7 to a pump (notshown). From this figure it can also be seen how the joints between theend of the centertube and the inside surfaces of the upper and lowershells, between the ends of the reinforcing weld posts, and between theperipheral flanges of the upper and lower shells can all be welded atthe same time in a single vibration welding operation.

FIGS. 4A through 4E illustrate the assembly of the transmission filterof the invention as follows: (1) First the upper shell 2 is turnedinside facing up as shown in FIG. 4A. (2) Next, the filter media element5 is placed on top of the upper shell and aligned by the welding poles10, which extend through alignment apertures 15 in the filter media 5 ascan be seen in FIG. 4B. (3) Then, the centertube 4 is placed on top ofthe filter media 5 surrounding the welding poles 10 as shown in FIG. 4C.This clamps the filter medium between one axial end face of thecentertube and the inside surface of the upper shell. The position ofcentertube 4 is such that it will be aligned with inlet 6 in lower shell3 when the lower shell is mated with the rest of the assembly. (4)Afterward, the filter media is folded into bag configuration andpositioned around the centertube as shown in FIG. 4D. An inlet hole 16is provided in the filter medium 5 which is aligned with centertube 4 sothat fluid from inlet 6 can freely enter the centertube. (5) Finally,the lower shell 3 is placed on top with the filter media capturedbetween the perimeter flanges 13 and 14 of the upper and lower shells,and the assembled parts are joined by a single vibration weldingoperation.

The foregoing description and examples have been set forth merely toillustrate the invention and are not intended to be limiting. Sincemodifications of the described embodiments incorporating the spirit andsubstance of the invention may occur to persons skilled in the art, theinvention should be construed broadly to include all variations withinthe scope of the appended claims and equivalents thereof.

1. A transmission filter comprising an first shell having an inletopening, a second shell having an outlet opening; said first and secondshells mating with each other to form a filter housing, a fluid perviouscentertube disposed in the filter housing between the first and secondshells such that the inlet opening communicates with the interior of thecentertube, at least one set of registering weld posts on interiorsurfaces of said first and second shells, and a filter medium clampedbetween the first and second shells and the centertube to form a filtersurrounding the centertube through which fluid moving from the inletopening to the outlet opening must pass.
 2. A transmission filteraccording to claim 1, wherein the filter material is clamped between thefirst shell and the center tube, between the second shell and thecentertube, and between the first and second shells to form a bag filtersurrounding the centertube.
 3. A transmission filter according to claim1, wherein the center tube has a mesh structure.
 4. A transmissionfilter according to claim 1, wherein the first and second shells and thecentertube are made of a thermoplastic synthetic resin material.
 5. Atransmission filter according to claim 4, wherein said synthetic resinmaterial is a thermoplastic polyamide material.
 6. A transmission filteraccording to claim 4, wherein said synthetic resin material isreinforced with glass fibers.
 7. A transmission filter according toclaim 4, wherein said synthetic resin material is PA66GF33.
 8. Atransmission filter according to claim 1, wherein said first and secondshells and said centertube are vibration welded together with saidfilter material between them in a single welding operation.
 9. A methodof making a filter comprising: providing mateable first and secondsynthetic resin shells with respective inlet and outlet openings, saidshells having at least one set of registering weld posts on insidesurfaces thereof; disposing a central portion of a filter web against aninside surface of one of said shells; disposing a fluid perviouscentertube against said central portion of said filter web to clamp saidfilter web against said one shell; wrapping said filter web around saidcentertube to form a filter bag; mating the other of said shells withsaid one shell with the weld posts on their inside surfaces registeringto form a filter housing, whereby a peripheral portion of said filtermaterial is clamped between said centertube and said other shell; andwelding the first and second shells and the centertube together in asingle welding step with the filter bag clamped between them such thatfluid moving from the inlet opening to the outlet opening must passthrough the filter bag.
 10. A method according to claim 9, whereinalignment apertures in the filter material are placed over the weldposts when the filter material is placed in the first shell to assureproper positioning of the resulting filter bag.
 11. A method accordingto claim 9, wherein said centertube has a mesh structure.
 12. A methodaccording to claim 9, wherein said first and second shells and saidcenter tube are made of injection molded thermoplastic synthetic resinmaterial.
 13. A method according to claim 12, wherein said syntheticresin material is a glass fiber reinforced polyamide material.